Aluminum is a metal which offers numerous advantages. It is light, capable of being easily drawn and die-stamped and conducts heat well. In addition, it is relatively economical. Because of these properties it is universally employed in industry, especially for producing cooking containers. However, it has drawbacks. First of all it is relatively soft, with the result that its surface is easily scratched. In household applications aluminum is frequently coated with a nonstick layer such as polytetrafluoroethylene or with a layer of enamel. However, the lifetime of these coatings is limited because aluminum is a substrate which is too soft. Furthermore, articles made of aluminum and in particular cooking containers tend to distort easily under the effect of the heat generated, for example, by an electric cooking plate or a gas burner.
To overcome this difficulty it is possible either to increase the thickness of the metal or to apply a sheet of stainless Steel to the aluminum wall, for example by hot stamping. However, in this case the cost of manufacture is appreciably increased and the heat conductivity is reduced, lengthening the cooking times.
Finally, aluminum utensils cannot be heated by induction, since this method of heating requires the use of containers made of magnetic metal such as ferritic stainless steel.
There are processes which make it possible to modify economically the characteristics of the surface of a metal. One such process consists in applying to the surface of the metal a grid of another metal, this grid being secured by die stamping. The grid may have all kinds of wire meshes, square ones, rectangular ones, hexagonal ones or others. It can also take the form of a planar sheet of perforated metal.
In the case of a perforated planar sheet the disadvantage arises from its lack of true anchorage in the surface material. In a shorter or longer term this could eventually give rise to a debonding of the sheet.